1. Field of the Invention
The present invention relates to an image forming apparatus, a fixing device for use in the image forming apparatus, and a separating member for use in the fixing device.
2. Description of the Related Art
A fixing device is used in image forming apparatuses, such as photocopiers or printers, to fix an image on a recording medium. However, sometimes the recording medium wraps around a fixing member in the fixing device. Japanese Patent Application Laid-open Nos. 2006-171551 and 2007-114415 disclose a conventional technology in which a separating member, such as a separating plate, is provided opposite to the fixing member to separate the recording medium from the fixing member.
A typical fixing device includes a fixing member and a pressing member that are in pressure contact with each other. The fixing member can be a fixing roller or a fixing belt. The pressing member can be a pressing roller, a pressing belt, or a pressing pad. Thus, a nip (fixing nip) is formed between the fixing member and the pressing member. The fixing member is heated by a heating unit such as a heater or an excitation coil. When a recording medium with an unfixed toner image thereon passes through the fixing nip, the toner is fixed onto the recording medium by virtue of heat and pressure.
A separating member is arranged downstream of the fixing member with respect to the running direction of the fixing member. The separating member and the fixing member are arranged such that there is a small gap between them. If a recording medium sticks to the fixing member, the separating member separates the recording medium from the fixing member so that the recording medium does not wrap around the fixing member.
How to maintain a small gap between the separating plate and the fixing member is an important issue. Japanese Patent Application Laid-open No. 2006-171551 discloses a fixing device in which positioning members are formed, by rolling or bending, on the two sides of the separating plate, and the separating plate is pushed toward the fixing member. Only the positioning members abut with the fixing member so that a small gap is maintained between the fixing member and parts of the separating plate other than the positioning members.
Japanese Patent Application Laid-open No. 2007-114415 discloses a fixing device that includes a position adjustment member that adjusts relative potions of a separating member and a fixing member. The position adjustment member adjusts the relative potions of the separating member and the fixing member such that a predetermined gap is always maintained between the separating member and the fixing member even if the fixing member thermally expands.
In the conventional fixing device, the positioning members are provided at locations that are considerably separated from a paper-passing area. Therefore, the fixing member and the separating member must be made longer in the width direction. As a result, the overall size of the fixing apparatus inevitably increases.